1. Field of the Invention
The invention relates to a process for forming contours in aramide flat structures, in particular in textile flat structures made from aramide yarns.
2. Discussion of Related Art
Aramide fibers find application in a number of areas in which high strength, low flammability, or good antiballistic action are required. Especially important among these application areas are those serving to provide protection of persons from the impact of projectiles, splinters, and the like.
For example, bullet- and splinterproof vests are manufactured from multiple superimposed aramide-fiber woven fabrics. Such fabrics also are used in antiballistic helmets and in various applications in property protection.
Due to the increasing use of female security personnel, protective clothing must be provided that conforms optimally to female body contours. The solutions to this problem proposed in the prior art, such as are described in U.S. Pat. No. 4,183,097, GB-A 2,231,481, U.S. Pat. No. 5,020,157, or U.S. Pat. No. 4,578,821, are expensive to manufacture and moreover do not offer the wearing comfort required by female security personnel.
Aramide flat structures, in particular aramide-fiber woven fabrics, also are often used in antiballistic helmets. In this case, the shaping is performed in part by deep-drawing of the fabrics embedded in a matrix resin, such as is described in U.S. Pat. No. 3,956,447, for example. In such processes, the treatment conditions must be adjusted to the resin of the matrix. This means that, depending on the type of resin, work is performed at relatively low temperatures. Irreversible imparting of shapes in the antiballistic fabrics embedded in or impregnated by resin and forming the actual antiballistic protective layers usually cannot be achieved under these conditions.
A contouring process for aramide sheets and films is described in U.S. Pat. No. 5,273,705. Work is performed using a high quantity of a swelling agent, which enables contouring. This process is not only very expensive, but it also raises environmental concerns due to some of the swelling agents proposed.